Neuroscience letters
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Neuroscience letters · Mar 2005
Comparative StudyCortical neuroplastic changes to painful colon stimulation in patients with irritable bowel syndrome.
The aim of this study was to model the cerebral generators following painful electrical stimulation of the sigmoid colon in 10 healthy controls and 10 patients with visceral pain due to the irritable bowel syndrome. The evoked brain potentials to 30 painful electrical stimuli from the sigmoid colon were recorded from 31 surface electrodes and subjected to electrical dipole source modelling. ⋯ The anterior cingulate dipole showed a more posterior position in patients than in control subjects. This finding suggests that the cortical representation of painful stimuli can be modified in presence of chronic visceral pain and that this change involves the anterior cingulate gyrus.
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Neuroscience letters · Feb 2005
Gender differences in electrical pain threshold responses to transcutaneous electrical nerve stimulation (TENS).
Gender differences in pain perception have been frequently discussed, but the documented gender-related pain-alleviating effects of non-pharmacological methods are sparse. In this study we aimed to investigate changes in electrical sensory thresholds and electrical pain thresholds, in response to high frequency transcutaneous electrical nerve stimulation, TENS, for 20 min in healthy women (n=29) and men (n=29). The thresholds were assessed pre-, during-, and post-TENS. ⋯ Significant additional individual variations were found in the women's responses of assessed electrical sensory and pain thresholds but not in the men's. It is concluded that both women and men responded with a significant increase of the electrical sensory threshold to high frequency TENS, but only women responded with increase of the electrical pain thresholds. The individual variation of the responses was greater in the women than in the men.
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Neuroscience letters · Feb 2005
Ketamine enhances the efficacy to and delays the development of tolerance to electroacupuncture-induced antinociception in rats.
Our previous studies have shown that 100 Hz electroacupuncture (EA) produced antinociception through the release of endogenous opioids (mainly dynorphin) and the activated kappa-opioid receptors in normal rats. Acupuncture is an effective treatment in relieving pain, but it develops tolerance after repeated administration. It has been reported that N-methyl-D-aspartate (NMDA) receptor antagonists could increase the antinociceptive effects induced by morphine and delay the development of tolerance to morphine but nothing has yet been described to reduce EA tolerance. ⋯ However, ketamine at either dose did not affect the basal nociceptive threshold (represented by tail-flick latency). (2) Ketamine at a dose of 5.0 mg/kg delayed the development of chronic tolerance to 100 Hz EA antinociception. We conclude that ketamine can enhance antinociception of 100 Hz EA and delay the tolerance to 100 Hz EA in rats. These results suggest that the development of 100 Hz EA tolerance to antinociception was mediated, at least in part, through peripheral NMDA receptors, which may be useful in improving the therapeutic effects of EA in the treatment of pain when EA tolerance occurs.
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Neuroscience letters · Feb 2005
Comparative StudyDivergent distribution of cytoglobin and neuroglobin in the murine eye.
Neuroglobin (Ngb) and cytoglobin (Cygb) are two vertebrate globins with yet poorly defined functions. Previous studies had demonstrated a high expression level of neuroglobin in the mammalian retina, being in line with a respiratory function. Here we show that in the mouse eye, cytoglobin is localised in fibroblasts of the ciliary processes and the choroidea. ⋯ Neuroglobin is localised in photoreceptor inner segments, the plexiform layers and the ganglion cell layer. The divergent distribution of neuroglobin and cytoglobin in the mammalian retina suggests distinct functions of these proteins in the vertebrate nervous system. While neuroglobin seems to be associated with oxygen consumption, a respiratory function of cytoglobin is unlikely.
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Neuroscience letters · Feb 2005
Comparative StudyErratum to "Noise-induced changes of neuronal spontaneous activity in mice inferior colliculus brain slices".
The inferior colliculus (IC) in vivo is reportedly subject to a noise-induced decrease of GABA-related inhibitory synaptic transmission accompanied by an amplitude increase of auditory evoked responses, a widening of tuning curves and a higher neuronal discharge rate at suprathreshold levels. However, other in vivo experiments which demonstrated constant neuronal auditory thresholds or unchanged spontaneous activity in the IC after noise exposure did not confirm those findings. Perhaps this can be the result of complex noise-induced interactions between different central auditory structures. ⋯ Noise-exposed animals showed a significant ABR threshold shift in the whole tested frequency range and a significant lower neuronal spontaneous activity in all investigated isofrequency laminae compared to controls. In both groups, the firing rate of 80% of IC neurons (approximately) increased significantly during the application of the GABA(A) receptor antagonist Bicucullin (10 microM). The present findings demonstrate a noise-related modulation of spontaneous activity in the IC, which possibly contribute to the generation of noise-induced tinnitus and hearing loss.